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Message-ID: <20240409225209.58102-3-kuniyu@amazon.com>
Date: Tue, 9 Apr 2024 15:52:08 -0700
From: Kuniyuki Iwashima <kuniyu@...zon.com>
To: "David S. Miller" <davem@...emloft.net>, Eric Dumazet
<edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni
<pabeni@...hat.com>
CC: Rao shoaib <rao.shoaib@...cle.com>, Kuniyuki Iwashima <kuniyu@...zon.com>,
Kuniyuki Iwashima <kuni1840@...il.com>, <netdev@...r.kernel.org>
Subject: [PATCH v1 net 2/3] af_unix: Don't peek OOB data without MSG_OOB.
Currently, we can read OOB data without MSG_OOB by using MSG_PEEK
when OOB data is sitting on the front row, which is apparently
wrong.
>>> from socket import *
>>> c1, c2 = socketpair(AF_UNIX, SOCK_STREAM)
>>> c1.send(b'a', MSG_OOB)
1
>>> c2.recv(1, MSG_PEEK | MSG_DONTWAIT)
b'a'
If manage_oob() is called when no data has been copied, we only
check if the socket enables SO_OOBINLINE or MSG_PEEK is not used.
Otherwise, the skb is returned as is.
However, here we should return NULL if MSG_PEEK is set and no data
has been copied.
Also, in such a case, we should not jump to the redo label because
we will be caught in the loop and hog the CPU until normal data
comes in.
Then, we need to handle skb == NULL case with the if-clause below
the manage_oob() block.
With this patch:
>>> from socket import *
>>> c1, c2 = socketpair(AF_UNIX, SOCK_STREAM)
>>> c1.send(b'a', MSG_OOB)
1
>>> c2.recv(1, MSG_PEEK | MSG_DONTWAIT)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
BlockingIOError: [Errno 11] Resource temporarily unavailable
Fixes: 314001f0bf92 ("af_unix: Add OOB support")
Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.com>
---
net/unix/af_unix.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index f297320438bf..9a6ad5974dff 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -2663,7 +2663,9 @@ static struct sk_buff *manage_oob(struct sk_buff *skb, struct sock *sk,
WRITE_ONCE(u->oob_skb, NULL);
consume_skb(skb);
}
- } else if (!(flags & MSG_PEEK)) {
+ } else if (flags & MSG_PEEK) {
+ skb = NULL;
+ } else {
skb_unlink(skb, &sk->sk_receive_queue);
WRITE_ONCE(u->oob_skb, NULL);
if (!WARN_ON_ONCE(skb_unref(skb)))
@@ -2745,11 +2747,9 @@ static int unix_stream_read_generic(struct unix_stream_read_state *state,
#if IS_ENABLED(CONFIG_AF_UNIX_OOB)
if (skb) {
skb = manage_oob(skb, sk, flags, copied);
- if (!skb) {
+ if (!skb && copied) {
unix_state_unlock(sk);
- if (copied)
- break;
- goto redo;
+ break;
}
}
#endif
--
2.30.2
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